The Question:

The Answer:

The site you are thinking of is not quite big enough to be
labeled a canyon—it's more of a gorge.

The Olduvai Gorge is a 30-mile long, 295-foot-deep ravine
located in Tanzania's Serengeti National Park
in east Africa. It is one of the most successful archaeological sites
in the world.

Some of the oldest human fossil remains have been unearthed
there. The most famous discovery occurred in 1959 when British
archeologist Mary
Leakey (along with her husband Louis) discovered remains of a
man they named "Nutcracker Man" (because of the extra-large molars)
that are believed to be 1.75 million years old.